Composition based on recycled polyethylene from cable waste

ABSTRACT

The invention is related to a polyethylene composition characterized in that it comprises a base resin and an inorganic mineral filler which is present in the composition in an amount of 1 to 50 wt % in respect to the weight of composition, wherein said base resin comprises: a) a first crosslinked polyethylene (PEX) having a gel content (measured according to ASTM D 2765:2006) in the range of 5% to 80% in respect to the weight of crosslinked polyethylene (PEX), said crosslinked polyethylene (PEX) being obtained from recycled wastes and b) a second polyethylene (PE) selected from virgin polyethylene and recycled polyethylene, or mixtures thereof. The invention is further related to a process for production of said polyethylene composition, and use of the polyethylene composition.

The present invention relates to a new polyethylene composition whichcomprises at least one polyethylene obtained from recycled wastematerial. Furthermore, the present invention relates to a process forproducing said polyethylene composition and the use of said compositionin infrastructure, engineering applications and packaging applications.

For the purposes of the present description and of the subsequentclaims, the term “recycled waste” is used to indicate the materialrecovered from both post-consumer waste and industrial waste. Namely,post-consumer waste refers to objects having completed at least a firstuse cycle (or life cycle), i.e. having already served their firstpurpose; while industrial waste refers to the manufacturing scrap whichdoes normally not reach a consumer. Respectively, the term “virgin”denotes the newly-produced materials and/or objects prior to first useand not being recycled.

Nowadays, the attempt of using polymers obtained from waste materialsfor the manufacturing of new products is of increasing interest andimportance for ecological reasons and for reducing costs.

In the field of cables, some efforts have already been undertaken inorder to use recycled polymer materials from cable waste, in particularpolyethylene or polyvinyl chloride obtained from waste cable sheaths.Said recycled polymer materials are generally used for making cablecoating layers.

An example of one of those efforts is JP2002/080671 which discloses apolyvinyl chloride-based recycled plastic composition obtained by mixingand melting covering plastics and sheaths of waste cables containing:(A) polyvinyl chloride and (B) polyethylene or silane-crosslinkedpolyethylene, with chlorinated polyethylene. The abovementionedpolyvinyl chloride-based resin is said to be useful for making cablesheaths.

JP2013045643 relates to insulated electric wire and cable which use alarge amount of waste-derived recycled material which containscrosslinked polyolefin homopolymer.

The recycled fraction containing cross-linked material has a gel contentof 40% or less and the recycled material is present in an amount of 75wt % or more in respect of the total composition.

CN102898768 discloses a flame retardant TPE composition made fromcross-linked polyethylene cable waste. The amount of cross-linked cablewaste is 40% or less and contains furthermore SBS block co-polymer(major part), phosphate flame retardants, extending oil, silane couplingagents and a very low amount of other auxiliaries. The prepared TPE isprovided with good flame retardance and other performances up tostandards.

However, the use of recycled polymer as described above in the prior artshows some drawbacks. In particular, it is presumed by the man skilledin the art that the use of recycled waste containing a crosslinkedpolyethylene (so-called ‘PEX’) fraction, may lead to poor mechanicalproperties compared to those obtained from virgin polyethylenematerials. The reason of this presumption is the concept thatcrosslinked fractions would be acting like a filler with poorcompatibility or adhesion to the thermoplastic parts of the compound.The weakest part of the compound is then the interface between thecross-linked particles and the thermoplastic matrix therefore theinterface will act as an initiation and propagation enabler for crazesand cracks. The mechanical properties become particularly worse whenhigh stresses, high speed (impact), high elongation and elevatedtemperatures come into play. Moreover, it is difficult to utilize arecycled waste material with high crosslinked content and/or havinglarge particles, especially with conventional melt processing methodsdue to lower processing speed and higher costs.

Consequently, due to cost reasons, poor mechanical properties, as wellas inferior processing properties the waste streams containingcrosslinked polyolefin, especially crosslinked polyethylene (PEX), aremore often used for energy recovery (e.g. incineration in a districtheating plant or for heat generation in the cement industry) but lessrecycled into new products.

Thus, there is still a need for developing methods to increase the useof recycled material into (higher value) products. Additionally, thereis a need for improved polymer materials containing crosslinkedpolyethylene obtained from recycled waste. Those improved materialscould advantageously be used in a broader application field than today.It is therefore the object of the present invention to overcome or atleast reduce the above mentioned disadvantages and to fulfillrequirements for higher value products, i.e. to extend the use inexisting and new applications.

This objective has been reached by providing a polyethylene compositioncharacterized in that it comprises a base resin and an inorganic mineralfiller which is present in the composition in an amount of 1 to 50 wt %in respect to the weight of composition, wherein said base resincomprises:

-   -   (a) a first crosslinked polyethylene (PEX) having a gel content        (measured according to ASTM D 2765:2006) in the range of 5% to        80% in respect to the weight of crosslinked polyethylene (PEX),        said crosslinked polyethylene (PEX) being obtained from recycled        waste, and    -   (b) a second polyethylene (PE) selected from virgin polyethylene        and recycled polyethylene, or mixtures thereof.

It has surprisingly been found that the polyethylene compositionaccording to the invention has an improved balance between stiffness, asshown by their flexural modulus, and good ductility in terms ofelongation at break as well as stress at break. Further, the compositionshows a surprisingly good impact performance. The composition in thepresent invention shows mechanical properties which at least havereduced the gap with the properties of virgin polyethylene. Anadditional advantage is that the carbon foot print of the articles thatare manufactured from recycled PEX is lower compared to products made ofvirgin products.

The term “base resin” denotes the entirety of polymeric components inthe polyethylene composition according to the invention. Optionally, thebase resin can comprise additional polymer components. Preferably, thebase resin consists of the first crosslinked polyethylene (PEX) and thesecond polyethylene (PE).

The term “crosslinked” in “crosslinked polyethylene (PEX)” can bedescribed and measured by its gel content. It should be noted that thecrosslinked polyethylene (PEX) in the present invention can be referringto a polyethylene composition comprising a fraction (A1) of fullycrosslinked polyethylene and a fraction of non-crosslinked thermoplasticpolyethylene (A2). The fully crosslinked polyethylene A1, generally hasa gel content in the range of 50% to 80%, preferably in the range of 55%to 70%, based on the weight of fraction A1. The gel content of thecrosslinked polyethylene (component A), is generally in the range of 5%to 80%, preferably in the range of 20% to 65%, more preferably in therange of 40% to 60% while being measured in respect of the total weightof PEX. Generally, the fraction A1 has a weight percentage of between20% and 100%, suitably of between 25% and 90%, more suitably of between30% and 80%, based on the weight sum of A1 and A2.

It is the essence of the present invention that the PEX is obtained fromrecycled waste. The PEX can be either recycled post-consumer waste,industrial PEX waste from the cable manufacturing process, oralternatively, a combination of both. Preferably, the PEX in the presentinvention is obtained from recycled waste by means of plastic recyclingprocesses known in the art. For example, said product may be obtained bymeans of a recycling process referred to as “PlastSep”, which originallyis developed by a company in the NKT group and described in thereference document “‘New Technology for Recycling of Plastics from CableWaste’, Paper presented at 8^(th) International Conference on InsulatedPower Cables, Versailles, 19-23 Jun. 2012, by Annika Boss et al.” Morepreferably, the PEX obtained from this kind of process is generally inthe form of granules with a diameter of less than 1 mm.

It is essential in the invention that the second polyethylene (PE) is anon-crosslinked thermoplastic polyethylene, which enables goodprocessability and good compounding results with the crosslinkedpolyethylene (PEX). The second polythylene can be selected from virginpolyethylene, recycled thermoplastic polyethylene or a mixture thereof.

The inorganic filler is an essential part of the composition accordingto the invention. Fillers are generally added to improve the mechanicalproperties, in particular the E-modulus.

In addition to the base resin and the inorganic filler, usual additivesfor utilization with polyolefins may be present in the polyethylenecomposition according to the invention. Examples of additives for use inthe composition are pigments or dyes (for example carbon black),stabilizers (anti-oxidant agents), anti-acids and/or anti-UVs,antistatic agents and utilization agents (such as processing aid agents)Generally, the amount of these additives is in the range of 0-8 wt %,preferably in the range of 0-5 wt %, more preferably in the range of0.01 to 3 wt %, based on the weight of total composition.

In the following the present invention is described in more detail.

In a preferred embodiment of the present invention, the weight ratio ofPEX to PE in the base resin is in the range of higher than 10:90 to90:10, preferably in the range of 10:90 to 70:30, more preferably in therange of 10:90 to 50:50.

In a preferred embodiment of the present invention, the crosslinkedpolyethylene (PEX) is obtained from the recycled material fromelectrical cable waste. More preferably, the PEX is obtained fromrecyclates of the high voltage (HV) and medium voltage (MV) power cablewaste.

It is known that the electrical cable waste is mainly a mixture ofvarious compositions including PE or PEX based compositions and PVCbased compositions. Therefore after the separating step in the recyclingprocess, a certain level of contamination caused by the PVC is probablypresent in the recycled PEX. This contamination leads to higher chlorinecontent in the recycled PEX, compared to the normal chlorine content invirgin polyethylene, especially the chlorine level in low pressurepolymerized PE such as LLDPE, MDPE and HDPE, where the chlorine level isdue to remaining catalyst residues.

By similar reasons, also contaminants from the cable conductor (eitheraluminum or copper) are generally present in the recycled PEX.

Therefore in a further preferred embodiment of the present invention,the crosslinked polyethylene (PEX) has a chlorine content in the rangeof 100 to 5000 ppm, preferably of 200 to 4000 ppm, most preferably of300 to 2000, measured with X-ray fluorescence analysis (XRF).

Furthermore, it is preferred that the crosslinked polyethylene (PEX) hasa copper content in the range of 20-500 ppm, more preferably in therange of 30 to 250 ppm, and/or an aluminum content in the range of500-15000 ppm, more preferably in the range of 1000-10000 ppm, measuredwith X-ray fluorescence analysis (XRF).

It is particularly preferred that the second polyethylene (PE) in thepresent invention is selected from virgin high density polyethylene(vHDPE), virgin medium density polyethylene (vMDPE), recycled highdensity polyethylene (rHDPE), recycled medium density polyethylene(rMDPE) and the mixtures thereof. The higher weight percentage of highdensity PE in respect of total base resin is preferred when higherstiffness of the material is desired. Preferably, when PE is selectedfrom virgin PE, it has a density of equal to or higher than 0.925 g/cm³,more preferably equal to or higher than 0.945 g/cm³; when PE is selectedfrom recycled PE, it comprises more than 80%, preferably more than 90%of polyethylene having a density of not lower than 0.925 g/cm³, morepreferably not lower than 0.945 g/cm³.

In the composition according to the present invention, preferablyinorganic mineral filler is present in an amount of at least 1 wt. %,more preferably at least 5 wt. %, still more preferably at least 8 wt.%, still more preferably at least 10 wt. % and most preferably at least12 wt. %. Furthermore, in the composition inorganic filler is present inan amount of at most 50 wt. %, more preferably of at most 45 wt. %,still more preferably at most 40 wt. %. Generally, in the compositionaccording to the present invention preferably inorganic mineral filleris present in a range of 1-50 wt %, preferably 5-45 wt %, morepreferably 8-42 wt %, most preferably 10-40 wt %. The filler of thecomposition according to the invention may comprise all inorganic fillermaterials as known in the art. The filler may also comprise a mixture ofany such filler materials. Examples for such filler materials areoxides, hydroxides and carbonates of aluminum, magnesium, calcium and/orbarium. Preferably, the filler comprises an inorganic compound of ametal of groups 1 to 13, more preferred groups 1 to 3, still morepreferred groups 1 and 2 and most preferred group 2, of the PeriodicTable of Elements. The numbering of chemical groups, as used herein, isin accordance with the IUPAC system in which the groups of the periodicsystem of the elements are numbered from 1 to 18. Preferably, theinorganic filler comprises a compound selected from carbonates, oxidesand sulphates. Preferred examples of such compounds are calciumcarbonate, talc, magnesium oxide, huntite Mg₃Ca(CO₃)₄, and hydratedmagnesium silicate, and kaolin (“China clay”), with particularlypreferred examples being calcium carbonate, magnesium oxide, hydratedmagnesium silicate, and kaolin (“China clay”).

Further preferred, the inorganic filler has a weight average meanparticle size, D50, of 25 micron or below, more preferably of 15 micronor below. Preferably, only 2 wt % of the filler has a particle size of40 microns or higher, more preferably only 2 wt % of the filler has aparticle size of 30 micron or higher.

In a preferred embodiment in which CaCO₃ is used as filler, preferablythe particles have a weight average mean particle size D50 of 6 micronor below, more preferably of 4 micron or below. The weight percentage ofthe filler in the total composition is preferred to be in the range of20-45%. In said embodiment, preferably only 2 wt % has a particle sizeof 8 micron or more, more preferably of 7 micron or more.

In another preferred embodiment in which talc is used as filler, theweight percentage of the filler in the total composition is preferred inthe range of 5-30%.

Generally, the purity of the filler is 94% or higher, preferably is 95%or higher and more preferably 97% or higher.

The inorganic filler may comprise a filler which has beensurface-treated with an organosilane, a polymer, a carboxylic acid orsalt etc. to aid processing and provide better dispersion of the fillerin the organic polymer. Such coatings usually do not make up more than 3wt % of the filler.

Accordingly, the polyethylene composition in the present invention isgenerally having a gel content in the range of 5-50 wt %, preferably7-40 wt %, more preferably 10-40 wt % in respect to the weight of thebase resin as measured according to ASTM D 2765:2006.

The composition according to the invention has a good balance ofstiffness and ductility as compared to prior art materials. It should benoted that the composition in the present invention is characterized notby any single one of the defined mechanical property features, but bytheir combination. By this combination of features it can advantageouslybe used in many application fields.

Accordingly, the polyethylene composition is therefore characterized inthat it has a flexural modulus determined according to ISO 178 of morethan 840 MPa, preferably more than 1000 MPa, more preferably more than1100 MPa and more than 1200 MPa.

In addition, the composition according to the present invention isfurther characterized in that it has an elongation at break determinedaccording to ISO 527-2 of more than 2%, preferably more than 3%, morepreferably more than 4%, most preferably more than 5%.

Furthermore, the composition in the present invention preferably has atensile stress at break determined according to ISO 527-2 of more than13 MPa, preferably more than 14 MPa, more preferably more than 15 MPa,most preferably more than 16 MPa.

Still further, the composition in the present invention preferably has ayield stress determined according to ISO 527-2 of more than 15 MPa,preferably more than 17 MPa, more preferably more than 19 MPa, mostpreferably more than 20 MPa.

Another embodiment of the present invention relates to a process forproducing the polyethylene composition comprising the steps of

-   -   a) feeding the ingredients into the inlet hopper of a        compounding unit;    -   b) compounding the ingredients which compounding is carried out        by homogenizing the ingredients fed into the inlet and raising        the temperature to above the melting point of the main        thermoplastic polymer ingredient, obtaining a mixture compound;    -   c) optionally cooling down the said mixture compound and        pelletizing.

Optionally, prior to the melted homogenizing step an additional drymixing step of all components can be applied.

Typically the melt temperature at the outlet of the compounding unit isaround 180-220° C. for polyethylene compounds in order to create asufficient mixing effect. The melt temperature at the outlet of thehomogenization unit could however be both higher and lower depending onthe needs. Particularly for compounds which are difficult to disperseand homogenize, the outlet temperature could be as high as 300° C. Forless demanding compounds and compounds which are sensitive to heatand/or when energy costs are of key importance, the homogenization wouldtake place below around 180° C. and lower, e.g. at 170° C. or 160° C. oreven lower. Particularly for recycled material with often additional,contaminating ingredients, the target would be to make the compoundingstep with an as low as possible melt temperature for keeping the cost ofthe product low, to increase the sustainability effort and forminimizing the additional odour and smell that is often generated withrecyclate containing compounds at high temperatures from e.g.contaminating ingredients in the recyclate.

Preferably, in the melt-homogenization step the PEX, PE and theinorganic filler and, optionally, other additives or other polymercomponents can be added to the inlet hopper of a compounding unit. Thecompounding unit could also be equipped with more than one inlet, e g.two inlets, and e.g. all the polymeric ingredients, optionally withadditives/antioxidants, could be fed in the first inlet and the fillerfed in the 2nd inlet further downstream the unit. Alternatively e.g. allthe polymers optionally with additives/antioxidants could be fed in thefirst inlet including part of the filler portion and the remaining partof the filler to be fed into the 2nd inlet further downstream.

The compounding unit could be any conventionally used compounding orextruder unit, preferably a co-rotating or counter-rotating twin screwextruder, or an internal mixer such as a Banbury type mixer or singlecrew extruder such as a Buss co-kneader or a conventional single screwextruder. Static mixers such as Kenics, Koch etc can also be used inaddition to the compounding or extruder units mentioned in order toimprove the distribution of the filler in the polymer matrix.

More preferably and especially for recycled materials the extruder orcompounding unit is equipped with one or more vacuum degassing unitsalong the screw or screws, with or without the use water strippingunits. The function of a water stripping unit is to add small amounts ofwater into the melt upfront of a mixing and a decompression and vacuumdegassing section. The resultant of this is to bring down both the smelland odour, as well as reducing the amount of volatiles in the finalcompound.

Further, the present invention is related to the use of a polyethylenecomposition as described hereinbefore for reducing the carbon foot printof the articles that are originators of the PEX. This is especiallyadvantageous in the field of infrastructure, engineering applicationsand packaging.

Still further, the present invention is related to the use of thepolyethylene composition according to the invention for reducing thecarbon foot print in the production of pipes and cables, traffic andconstruction elements as well as packaging materials.

Preferably, the present invention is related to the use of thepolyethylene composition according to the invention for reducing thecarbon foot print in the production of objects listed below:

-   -   Non-pressure underground pipes and system parts for road and        land drainage, for storm water applications,    -   Cable protection, cable conduits both for underground        applications, for road and rail applications, cable channels,        cable marking and cable digging protection sheets and pipes,    -   Road (and rail) side structure, include all types of auxiliary        structures found along roadways (e.g., signs, roadway lighting        systems, rail and barrier systems, sound and wind barriers,        crash cushions etc.),    -   Floor and floor protection, indoor and outdoor,    -   Roofing materials and ingredient for roofing materials.

The following examples serve to further illustrate the present inventionwithout limiting it.

EXAMPLES AND MEASURING METHODS

The following definitions of terms and determination methods apply forthe above general description of the invention as well as to the belowexamples unless otherwise defined.

1. Measuring Methods

Gel Content (wt %): is measured according to ASTM D2765-90 using asample consisting of the polyethylene composition of the invention(Method A, decaline extraction).

X-ray Fluorescence analysis (XRF): The elemental content was analysed bywavelength dispersive XRF (AXS S4 Pioneer Sequential X-ray Spectrometersupplied by Bruker). The pellet sample was pressed to a 3 mm thickplaque (150° C. for 2 minutes, under pressure of 5 bar and cooled toroom temperature). Generally, in XRF method, the sample is irradiated byelectromagnetic waves with wavelengths 0.01-10 nm. The elements presentin the sample will then emit fluorescent X-ray radiation with discreteenergies that are characteristic for each element. By measuring theintensities of the emitted energies, quantitative analysis can beperformed. Here, the analysis has been done with a standard-free programwhere the 28 most common elements are detected and the concentrations ofthe detected elements are calculated based on a CH₂ matrix.

Flexural modulus: is determined on compression molded sample accordingto ISO 178 at 23° C., the sample thickness is mentioned below in thesample preparation.

Tensile testing: Tensile stress and modulus for the examples 1E1-5,CE3-5 were determined on compression moulded specimens according to ISO527-2 at 50 mm/min and 23° C., the sample thickness is mentioned belowin the sample preparation. Tensile test for the examples 1E6 and CE1, 2,6-8 was measured according to ISO 527-2 on injection moulded specimensas described in EN ISO 1872-2 (80×10×4 mm), wherein the crosshead speedfor testing the modulus was 1 mm/min and crosshead speed for testing thetensile strength and elongations was 50 mm/min.

Test specimen produced as described in EN ISO 1872-2 (the produced testspecimens were 10 multipurpose test specimen of type B according to ISO3167).

Charpy impact test: The charpy notched impact strength (Charpy NIS) ismeasured according to ISO 179 1eA at 23° C. and −20° C. respectively.The impact is measured on samples prepared from injection moldedspecimens as described in EN ISO 1872-2 (80×10×4 mm)

2. Examples

Base Resin

PEX:

PEX RECYCLATE 1 MM: a crosslinked polyethylene which is entirelyrecycled post-consumer cable waste is in the form of granules smallerthan 1 mm in diameter. The PEX has a gel content of about 50 wt %. Table1 shows the analytical result of PEX RECYCLATE 1 MM

TABLE 1 Elemental content determined by XRF analysis on three pressed 3mm plaques. Zinc 48 ppm Titan 82 ppm Calcium 955 ppm Sulphur 125 ppmSilicon 316 ppm Aluminium 1450 ppm Magnesium 191 ppm Chlorine 389 ppmCupper 59 ppm Iron 61 ppm Nickel <5 Phosphorus <5 Chromium <5 Potassium<5 Vanadinium <5

HE3450: a virgin high density polyethylene bimodal copolymer,commercially available from Borealis with a melt flow rate (MFR2) of 0.5g/10 min, according to ISO 1133 (190° C., 2.16 kg) and a density of0.950 g/cm³.

KRUTENE-HD: a recycled high density polyethylene in the form of pellets,commercially available from KRUSCHITZ GMBH with a melt flow rate (MFR2)of 0.49 g/10 min, according to ISO 1133 (190° C., 2.16 kg), and densityof 0.950 g/cm³.

Inorganic Filler

CALCITEC M/5: Calcium carbonate filler which had a weight average meanparticle size D50 of 5.0 microns with only 1 wt % having a particle sizeof 19 micron or higher, and a purity of 99% CaCO₃.

MISTRON 75-6 A: Talc filler which has a weight average mean particlesize D50 of 4.0 microns with only 2 wt % having a particle size of 20micron or higher and a purity of 98% Mg-silicate.

Compounding and Preparation of Injection Moulded and Compression MouldedSamples

The predetermined amount of PEX and PE was mixed with the inorganicfiller in a Brabender 350E mixer with a roller element at a temperatureof 180° C. for 10 min. The screw speed was 40 RPM. The equipment waspurged with nitrogen during the homogenisation to minimise degradation.

Injection Moulding:

The test specimens for the examples 1E6 and CE1, 2, 6-8 were injectionmoulded using a machine Engel e-motion 310/55HL with a 35 mm screw at210° C.

Compression Moulding:

The test specimens for the examples 1E1-5, CE3-5 were compressionmoulded. The raw materials were transferred to a compression mouldingdevice to produce about 2-4 mm thick plates from which the samples weremachined into the sample type specified for the particular test method,respectively. 2 mm thick samples were used for the tensile measurementsand 4 mm thick samples were used for measurements in bending mode.Compression moulding conditions: 200° C. at low pressure for 10 minutesand for 5 minutes at 614 N/cm² and cooling down at 15° C./min. Table 2and Table 3 list the composition recipes and mechanical properties forsix inventive examples 1E1 to 1E6 and eight comparative examples CE1 toCE8. The inventive examples show a surprisingly good combination ofmechanical properties comparing to the CE2-8 examples and bring themechanical properties closer to CE1.

TABLE 2 Composition recipe and mechanical properties of the inventivesamples IE1 IE2 IE3 IE4 IE5 IE6 HE3450-H (0.950 g/cm³) KRUTENE-HD 30 4530 45 60 80 (0.952 g/cm³) PEX RECYCLATE 1 MM 30 30 45 30 30 10 CALCITECM/5 40 25 MISTRON 75-6 A 25 25 10 10 sum 100 100 100 100 100 100 Stressat break (MPa) 13.2 14.7 14.9 19.6 18.0 11.2 Yield stress 15.4 17.8 15.720.6 18.5 — Flexural modulus (MPa) 1120 950 1040 1330 940 — EAB (%) 5.412.2 5.3 3.9 7.2 40.0 Charpy NIS 23° C. (kJ/m²) — — — — — 20.1 CharpyNIS −20° C. (kJ/m²) — — — — — 4.4

TABLE 3 Composition recipe and mechanical properties of the comparativesamples CE1 CE2 CE3 CE4 CE5 CE6 CE7 CE8 HE3450-H 100 80 (0.950 g/cm³)KRUTENE-HD 55 80 60 100 (0.952 g/cm³) PEX 60 75 45 RECYCLATE 1 MMCALCITEC M/5 40 40 MISTRON 75-6 A 20 25 20 sum 100 100 100 100 100 100100 100 Stress at break 23.1 4.6 10.7 10.2 6.6 5.3 13.0 8.5 (MPa) Yieldstress 19.6 — 11.9 10.5 18.1 — — — Flexural modulus 820 — 590 400 620 —— — (MPa) EAB (%) 647.0 82.0 8.4 8.9 63.8 53.0 13.9 144.0 Charpy NIS56.0 34.2 — — — 8.0 16.5 18.0 23° C. (kJ/m²) Charpy NIS 16.9 10.4 — — —3.9 5.8 4.0 −20° C. (kJ/m²)

The invention claimed is:
 1. A polyethylene composition comprising abase resin and an inorganic mineral filler which is present in thecomposition in an amount of 1 to 50 wt % in respect to the weight ofcomposition, wherein the inorganic mineral filler is selected from CaCO₃and Talc, wherein said base resin comprises: a) a first crosslinkedpolyethylene (PEX) having a gel content (measured according to ASTM D2765:2006) in the range of 5% to 80% in respect to the weight ofcrosslinked polyethylene (PEX), said crosslinked polyethylene (PEX)being obtained from recycled waste, and b) a second polyethylene (PE)selected from virgin polyethylene and recycled polyethylene, or mixturesthereof.
 2. Polyethylene composition according to claim 1, wherein theweight ratio of PEX:PE in the base resin is in the range of from higherthan 10:90 to 90:10.
 3. Polyethylene composition according to claim 1,wherein the crosslinked polyethylene (PEX) is obtained from recycledwaste wherein the waste is selected from electrical cable waste. 4.Polyethylene composition according to claim 1, wherein the crosslinkedpolyethylene (PEX) has a chlorine content in the range of 300 to 2000ppm measured with X-ray fluorescence analysis (XRF).
 5. Polyethylenecomposition according to claim 1, wherein the crosslinked polyethylene(PEX) has: a) a copper content in the range of 20-500 ppm and/or b) analuminum content in the range of 500-15000 ppm, measured with X-rayfluorescence analysis (XRF).
 6. Polyethylene composition according toclaim 1, wherein the second polyethylene (PE) is selected from virginhigh density polyethylene (vHDPE), virgin medium density polyethylene(vMDPE), recycled high density polyethylene (rHDPE), recycled mediumdensity polyethylene (rMDPE) and the mixtures thereof.
 7. Polyethylenecomposition according to claim 1, wherein the composition has a gelcontent in the range of 10 to 40 wt % in respect to the weight of thebase resin as measured according to ASTM D 2765:2006.
 8. Polyethylenecomposition according to claim 1, wherein the composition has a flexuralmodulus determined according to ISO 178 of more than 840 MPa. 9.Polyethylene composition according to claim 8, wherein the compositionadditionally has an elongation at break determined according to ISO527-2 of more than 2%.
 10. Polyethylene composition according to claim8, wherein the composition has a tensile stress at break determinedaccording to ISO 527-2 of more than 13 MPa.
 11. Polyethylene compositionaccording to claim 8, wherein the composition has a yield stressdetermined according to ISO 527-2 of more than 15 MPa.
 12. Process forproducing a polyethylene composition according to claim 1, wherein thesaid process comprising the steps of: a) feeding the ingredients intothe inlet hopper of a compounding unit; b) compounding the ingredientswhich compounding is carried out by homogenizing the ingredients fedinto the inlet and raising the temperature to above the melting point ofthe main thermoplastic polymer ingredient, obtaining a mixture compound;and c) optionally cooling down the said mixture compound andpelletizing.
 13. Process for producing a shaped article comprising apolyethylene composition according to claim 1, wherein the said processcomprises the additional step of shaping the said polyethylenecomposition with a moulding step.